This invention relates to an arrangement for spinning staple fibers into a yarn of the type having a feeding and opening device which opens up fiber material supplied in the form of a sliver into individual fibers. A disk-shaped collecting element takes over the separated yarns and has a rotating, air permeable collecting surface which is aligned approximately tangentially with respect to an opening roller of the feeding and opening device. A suction device is assigned to the collecting surface on the side facing away from the opening roller and facing the collecting surface by means of a suction slot which tapers in the circumferential direction to a withdrawal point which is followed by a twisting element and a withdrawal device.
In an arrangement of the initially mentioned type (German Patent Document DE-A 36 24 190), the drafting of the fed fiber material to the desired yarn size takes place with the opening-up into individual fibers. The separated fibers are then guided to the collecting surface already in an amount which corresponds to the yarn size to be spun so that a subsequent doubling is no longer required. The separated fibers are bundled to form a fiber composite only transversely to the direction of their continued transport. In the case of the known construction, a flat, plane disk (FIG. 25) is arranged as the collecting element from which the fiber composite is withdrawn against the rotating direction of the disk while a twist is introduced. In this construction, the fibers are held exclusively by the effect of the suction device against the centrifugal force which exists because of the rotation of the disk. In another embodiment, the fibers are fed from the outside onto a conical rotation body which is provided with a suction device on the inside. In this embodiment, the fibers are also held against the centrifugal forces only by the suction effect. In another embodiment (FIG. 27), the fibers are fed to the interior surface of a cylindrical collecting element. In this construction, the interior surface supports the fibers against the centrifugal force. In this case, the collecting of the fibers takes place exclusively by means of the effect of the suction slot tapering in the transport direction.
It is also known (French Patent Document FR-A 23 60 695) to feed the separated fibers, by way of a fiber feeding duct, following an opening roller of a feeding and opening device, into a rotor which has a wall which ascends toward the outside in a truncated-cone-shaped manner. As a result of the centrifugal force, the fibers are to ascend over the edge of the rotor after which they are collected in a stationary collecting groove from which they are withdrawn through a rotating element.
It is also known (European Patent Document EP-B 0 236 324) to feed the fibers separated by a feeding and opening device to a moving collecting surface on which they are doubled so that the desired yarn size is obtained. The collecting surface will then advance the fiber composite to a withdrawal point at which, while being rotated at the same time, the fiber composite is withdrawn into the direction in which it is fed. In this case, the withdrawal speed corresponds essentially to the speed at which the fiber composite is fed by the collecting surface.
It is an object of the invention to provide an arrangement of the initially mentioned type in which the centrifugal forces participate in the compacting of the separated fibers to a fiber composite while, however, the holding of the fibers against the centrifugal forces does not have to be carried out exclusively by the effect of the suction device.
This object is achieved according to preferred embodiments of the present invention in that the disk-shaped collecting element is provided with a conical area which ascends toward the outside and is constructed as a fiber collecting surface.
In this construction, the centrifugal forces participate in the compacting of the separated fibers to a fiber composite while, however, at the same time, the fiber collecting surface supports the fibers at least partially against the centrifugal forces so that a lower air throughput is required for the suction device.
In a further development of the invention, it is provided that the collecting element is constructed in the shape of a bowl, the edge area of which serves as the fiber collecting surface. In a further development of the invention, it is provided that the bowl has a vertical axis of rotation and the fiber collecting surface ascends toward the outside and upward. This has the advantage that the gravitational force affecting the fibers partially counteracts the centrifugal forces so that a further reduction of the power consumption is possible with respect to the suction device.
In a further development of the invention, it is provided that the fiber collecting surface is bounded toward the outside by means of a collecting groove. This collecting groove is used on the one hand as a safety measure to prevent fiber losses by a throwing-off of fibers from the collecting surface while, on the other hand, it improves the collecting operation. It is preferable and expedient for the suction slot to end in front of the withdrawal point. As a result, it is ensured that all fibers are collected in the collecting groove.
In a further development of the invention, it is provided that a roller is arranged at the withdrawal point of the fiber collecting groove which is situated opposite the fiber collecting surface. The withdrawal point can be exactly defined by means of this roller.
In a further development of the invention, it is provided that the roller is loaded by means of an elastic contact pressure device in the direction of the collecting surface.
The roller presses against the collecting surface with a relatively slight force in the order of 10N. This has the result that the twist introduced by the twisting element is a false twist so that a yarn is created which in principle corresponds to a yarn manufactured by pneumatic false-twist spinning. However, in contrast to the known pneumatic false-twist spinning which operates with drafting units, because of the feeding and opening device, an arrangement is achieved that has a much higher capacity. When the contact pressure is adjusted to be even lower or when the roller is left out completely, the twisting element introduces a true twist into the fiber composite so that then a true-twisted yarn is created.
In a further development of the invention, it is provided that the withdrawal direction of the withdrawal device is essentially tangential to the fiber collecting surface in the area of the withdrawal point and has a moving component which continues the moving component of the fiber collecting surface at the withdrawal point. As a result, it is avoided that a significant deflection of the fiber composite occurs in this area which may cause a tangling of the fibers.
In a further development of the invention, it is provided that a driven suction roller is arranged between the withdrawal device and the withdrawal point, the suction area of which is directed at the travelling yarn and the circumferential speed of which in the travelling direction of the yarn is higher than the withdrawal speed of the withdrawal device. This suction roller takes along, at an increased speed, edge fibers which project or spread away from the fiber composite, that is, at a speed which is higher than the speed of the core of the fiber composite. These spread-away edge fibers which are taken along at an increased speed will then, at the time of the opening-up of the false twist, form wind-around fibers behind the twisting element which provide strength to the spun yarn and which are wound around the yarn core in a very uniform manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.